The invention relates to a corona ignition system for the igniting of fuel in a combustion chamber of an internal combustion engine.
US 2011/0114071 A1 discloses a corona ignition system, by which a fuel-air mixture can be ignited in a combustion chamber of an internal combustion engine by means of a corona discharge generated in the combustion chamber. This corona ignition system has an ignition electrode which is situated in an insulator. The ignition electrode, together with the insulator and a sleeve surrounding the insulator, forms an electrical capacitor. This capacitor is part of an electrical resonant circuit of the corona ignition device, which is excited with a high frequency AC voltage for example from 30 kHz to 50 MHz. Thereby, a voltage excess results at the ignition electrode, so that a corona discharge forms at the latter.
The high frequency AC voltage is generated by a high frequency generator, the input voltage of which is generated by a transformer from the on-board electrical system of the vehicle.
A corona discharge forms ions and radicals in a fuel-air mixture in the combustion chamber of an engine. When a critical concentration of ions and radicals is reached, the fuel-air mixture ignites. The rate at which ions and radicals are produced depends on the size of the corona discharge and its electrical output. The size and output of a corona discharge can be increased only up to a critical limit. If this limit is exceeded, the corona discharge transitions into an arc discharge or spark discharge.
Corona ignition systems are generally controlled so that the corona discharge is as large as possible, so that fuel-air mixture can be ignited as rapidly as possible and therefore the moment of ignition can be predetermined as precisely as possible, but a breaking through of the corona discharge into an arc or spark discharge is prevented.